The significance of region-specific habitat models as revealed by habitat shifts of grey-faced buzzard in response to different agricultural schedules.

To determine large scales habitat suitability for focal species, habitat models derived from one region are often extrapolated to others. However, extrapolation can be inappropriate due to regional variation of habitat selection. Accounting for the ecological mechanisms causing such variation is necessary to resolve this problem. We focused on grey-faced buzzards in agricultural landscapes of Japan, which show geographically different habitat selection. To determine whether this variation is caused by the difference in climatic conditions at geographical scales or the difference in agricultural practices at smaller regional scales, we surveyed distributions of buzzards and their major prey (frogs/orthopterans) in regions differing in rice-transplanting schedules within the same climatic zone. We found that buzzards preferred paddy-forest landscapes in the early transplanting regions, but grassland-forest landscapes in the late transplanting regions. Frogs were more abundant in the early transplanting regions due to flooded paddies, while the abundance of orthopterans did not differ. The regional variation in habitat selection of buzzards may be due to different prey availabilities caused by different agricultural schedules. We propose that habitat suitability assessments of organisms inhabiting agricultural landscapes should consider differences in production systems at regional scales and such regional partitioning is effective for accurate assessments.

Analysis of the Genetic Diversity and Structure of the Grey-Faced Buzzard (Butastur indicus) in Japan, Based on mtDNA.

The grey-faced buzzard (Butastur indicus) is a raptor that inhabits East Asia, including Japan. Because the number of individuals has decreased by 75% over the last 40 years, this species is classified as vulnerable (VU) in Japan. In the present study, wesought to reveal the genetic structure of the Japanese grey-faced buzzard population at several breeding sites, and to assess the levels of genetic diversity within the Japanese population. We sequenced 555 bp of the mitochondrial DNA of 96 individuals sampled during the breeding season at 18 sites, and 11 individuals sampled during the winter season at one site. In total, 21 variable sites were found in the control region, and we detected 26 haplotypes among the 107 individuals. Fukuoka represented the core breeding area for grey-faced buzzards, as half of all haplotypes were detected there. Four unique haplotypes were detected in the overwintering area. The results of the network and mismatch distribution analyses indicated that the grey-faced buzzard has not experienced a genetic bottleneck in the past, but did experience recent population expansion. In addition, comparisons with other raptors revealed rich genetic diversity in the grey-faced buzzard population. Our results indicate that conservation of both breeding and wintering areas is important for the protection of the grey-faced buzzard.

Context Dependent Effect of Landscape on the Occurrence of an Apex Predator across Different Climate Regions.

In studies of habitat suitability at landscape scales, transferability of species-landscape associations among sites are likely to be critical because it is often impractical to collect datasets across various regions. However, limiting factors, such as prey availability, are not likely to be constant across scales because of the differences in species pools. This is particularly true for top predators that are often the target for conservation concern. Here we focus on gray-faced buzzards, apex predators of farmland-dominated landscapes in East Asia. We investigated context dependency of "buzzard-landscape relationship", using nest location datasets from five sites, each differing in landscape composition. Based on the similarities of prey items and landscape compositions across the sites, we determined several alternative ways of grouping the sites, and then examined whether buzzard-landscape relationship change among groups, which was conducted separately for each way of grouping. As a result, the model of study-sites grouping based on similarities in prey items showed the smallest ΔAICc. Because the terms of interaction between group IDs and areas of broad-leaved forests and grasslands were selected, buzzard-landscape relationship showed a context dependency, i.e., these two landscape elements strengthen the relationship in southern region. The difference in prey fauna, which is associated with the difference in climate, might generate regional differences in the buzzard-landscape associations.